The invention relates to a glass rupture disk and, more particularly, to a glass rupture disk and mounting apparatus with controllable rupture characteristics positioned to selectively restrict fluid flow in a well.
In the general process for drilling and production of oil and gas wells, at that point in the process where a hydrocarbon formation has been located at a particular depth, normally an exterior casing would be lowered down the bore hole through the area of production, known as the production zone. The exterior casing is perforated with the use of a perforating gun or the like. Using electric wire line and setting tools, or some other means, a permanent type packer, referred to as a xe2x80x9csump packerxe2x80x9d is usually set below the perforations. Subsequently, an internal tubing string, together with sand screen and blank pipe, packer and packer extension, hydraulic setting tool, cross-over tool, and wash pipe, are positioned within the exterior casing to engage with the xe2x80x9csump packerxe2x80x9d. The annulus between the sand screen and the exterior perforated casing is packed off, utilizing certain procedures. This packing off is necessary so that the interior tubing would be utilized to carry the recovered hydrocarbons to the surface. The area around the perforations is prepared, so that the flow of hydrocarbons can commence.
After gravel packing is complete, oftentimes the well can not necessarily be pressure balanced. The formation, under these conditions, can tend to absorb the well fluid into the production zone or the fluid in the zone can tend to flow into the well. In either case, this could lead to unacceptable (a) loss of expensive well fluid, (b) damage to the formation, (c) danger of a potential well blow-out or co-mingling of formation fluids. There is a need in the art for a device, such as a valve or rupture disk, that can prevent the movement of fluids within the well and under varying degrees of pressure differential within the well.
In conventional practice, when a well conduit is desired to be temporarily closed off, it is common to set a plug within the conduit to preclude the flow of fluids at the preferred location. Alternatively, a temporary plug can be installed in the lower end of the production tubing to permit tests for the pressure bearing integrity of the tubing. Additionally, the plug can permit the selective pressurization of the tubing to permit the operation of pressure sensitive tools within the tubing. Regarding oil and gas wells, there are many types of plugs that are used for different applications. As an example, there are known removable plugs typically used during cementing procedures that are made of soft metals that may be drilled out of the conduit after use. Plugs that can be removed from a well intact are referred to as xe2x80x9cretrievablexe2x80x9d plugs. Removal, however, requires mechanical intervention from the surface of the well. Common intervention techniques include re-entry into the well with wireline, coiled tubing, or tubing string. Because other well operations cannot be performed during such work, the retrieval of the temporary plug delays the well operations and adds additional cost to the well operations.
After a conventional type plug has been set and it subsequently becomes necessary to reestablish flow, any tools that have been associated with the plug during its use must be removed or xe2x80x9cpulledxe2x80x9d from the well to provide access to the plug for the removal process. The pulling of tools and removal of the plug to reestablish flow within a downhole conduit often entails significant cost and rig downtime. It is, therefore, desirable to develop a plug that can be readily removed or destroyed without either significant expense or rig downtime.
Known conduit plugs incorporating frangible elements that must be broken from their plugging positions include frangible disks that are stationarily located within tubular housings and flapper type elements. One technique uses a phenolic disk packed with explosives. Breakage can be initiated by piercing the plug to cause destructive stresses within the plug""s body, mechanically impacting and shattering the plug, or increasing the pressure differential across the plug until the plug is xe2x80x9cblownxe2x80x9d from its seat. After breakage has occurred, the resulting shards or pieces must be washed out of the well bore with completion fluid or the like in many situations. Because most known designs call for a relatively flat plug to be supported about its periphery, the plug commonly breaks from the interior outwardly and into relatively large pieces that can interfere with other well completion activities.
Another temporary plug technique uses a glass disk to temporarily seal the well tubing. When ruptured with fluid pressure, explosives, or mechanical devices, the glass fractures into relatively small fragments to open the tubing bore. Although the glass fragments are generally smaller than the fragments left by a phenolic disk, the glass disks are brittle and do not reliably support large differential fluid pressures within the well. The glass surfaces are also easily damaged leading to significant strength degradation of the glass. As a result, the glass disks can inadvertently rupture, leading to failure of the completion operations.